The human body is designed to “fight” viruses and bacteria that can come from the environment. Immunity to certain diseases usually occurs after experiencing that disease. However, there are substances that help the body, in advance, to fight against these infections. Most of those substances are in vaccines.
These substances have different ways of acting in the person’s body:
- The alive virus vaccine introduces a small part of the virus to which one wants to immunize, but this exposure is controlled and the virus portion has been weakened so as not to cause harm to the person.
- Killed or inactivated vaccines, of which a protein is formed, from fragments of the virus.
- Toxoid vaccines contain a poison that allows the immune system to fight effectively against the virus.
- And finally, biosynthetic vaccines, which resemble the virus so that the body at the time of infection recognizes it as a threat and uses all its resources to destroy it.